This invention relates to a valve assembly. While the valve assembly lends itself to various applications, it is particularly useful in connection with a gear pump of the type disclosed in Swedberg U.S. Pat. No. 3,556,901. The gear pump of the Swedberg patent is especially designed to supply fuel to an oil burner.
A pump of the type disclosed in the Swedberg patent includes a diaphragm-operated valve assembly which controls opening and closing of the main regulating valve for controlling the supply of fuel from the pump to the oil burner. Such a valve assembly includes a valve member adapted to open and close a control port. A spring engages one side of the valve member and urges the latter to an open position with respect to the control port. The other side of the valve member engages a flexible diaphragm which is responsive to the output pressure of the pump. When that pressure exceeds a predetermined magnitude, the diaphragm causes the valve member to close the control port against the bias of the spring and effect opening of the main regulating valve. When the pump is shut down, the spring snaps the valve member to a position opening the control port and effecting rapid closure of the regulating valve.
The valve assembly of the Swedberg patent utilizes a Belleville spring to urge the valve member to an open position with respect to the control port. In other valve assemblies, a conical coil spring is used to urge the valve member to its open position (see, for example, Harwath U.S. Pat. No. 5,145,328). Such a spring incorporates multiple coils which are compressed when the valve member is forced to its closed position against the valve seat by the pressure exerted on the flexible diaphragm. In conventional coil springs which have been used previously, the two end coils of the spring are disposed in substantially parallel planes and extend substantially perpendicular to the longitudinal axis of the spring. It has been found that, when the spring is compressed, the coils cause the valve member to assume a cocked position with respect to the valve seat. As a result, the control port may not be completely sealed by the valve member, and such incomplete sealing creates leakage through the port and reduces the efficiency of the pump.